A .sigma.-receptor has been defined as one of the opioid receptor including with .mu.-, .delta.-, .kappa.- and .epsilon.-receptor. At present, the .sigma.-receptor is classified not as opiate but as an independent receptor because an opioid antagonist naloxon has no affinity to a .sigma.-receptor.
Pharmacological action through .sigma.-receptor has not been investigated. Psychotomimetic drug phencyclidine has affinities for .sigma.-receptor other than NMDA receptor, and antipsychotic drug haloperidol has been known to bind strongly .sigma.-receptor other than dopamine receptor. Therefore, .sigma.-receptor may participate psychic function, however no specific drug for .sigma.-receptor has been reported.
British Patent 852971 (1959), Acta pharmacol. et Toxicol., 17, 277-287 (1960) and Acta Chemica Scandinavica, 17, 2069-2078 (1963) disclosed N-substituted phenylalkyl camphidine derivative of the formula ##STR3## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are H, Cl, --NO.sub.2, --NH.sub.2, --CH.sub.3, --OCH.sub.3 or --OH and m is an integer of 1-3, and indicated the usefulness for depressor activity upon the central nervous system and tranquilizer.
Yakugaku Zasshi, 84(10), 918-929 (1964) disclosed N-substituted phenylalkyl camphidine derivative of the formula ##STR4## wherein R' is H, Cl or --NH.sub.2 and m is 1 or 2 and almost no effect of analgesic action was reported.
In the above prior arts, no usefulness of these prior known compounds on apomorphine induced climbing model, a frequently used animal model for schizophrenia, has disclosed.
Creating the specific drug for .sigma.-receptor and finding the novel pharmacological effect are important for developing new type of drugs.